Circuit interrupter



Oct. 21, 1941. J. M. WALLACE CIRCUIT INTERRUPTER File'd Feb. 25, 1959Bari-Aid H 1 9, 3 7' 5 3 a z x 4 w W z 1 .4 4 M 41M. III... IIIIH. ww mM a M x B I a w 4 f 1|- B a J INVENTOR James Mil aliens:

BY q 3 ZTTORNE;

Patented Oct. 21, 1941 CIRCUIT INTERRUPTER James M. Wallace, Braddock,Pa., asslgnor to Westinghouse Electric & Manufacturing Company, EastPittsburgh, Pa., a corporation of Pennsylvania Application February 23,1939, Serial No. 257,879

22 Claims.

This invention relates to improvements in circuit interrupters and, moreparticularly, to power fuse devices of the high-voltage high-currenttype. In recent years, high voltage power fuses of the expulsion typehave been used more extensively in electrical circuits and to a certainextent have replaced the more costly circuit breaker structures inapplications where overload protection is the prime objective. However,high ower fuses of the expulsion type have bee ated in their applicationto power circuits in which the normal load current does not exceed 400amperes. The usual practice of using a fuse in a branch or feedercircuit protected by either another fuse or a circuit breaker makes itnecessary to provide fuse structures having different operatingcharacteristics so as to permit selective operation. A more extensiveuse of power fuses as protective devices in power circuits has beenprevented by the lack of a high current fuse structure having a fastoperating characteristic.

The main object of the invention is to provide 7 a power fuse structureof the high voltage type having a higher current carrying capacity thandevices heretofore known in the art.

A further object of the invention resides in the provision of a powerfuse of the foregoing type having a fast operating characteristic whichis comparable in operating time to known fuse devices of materiallylower current rating.

Another object of the invention resides in increasing the normal loadcapacity .of a high voltage power fuse without materially increasing theexternal dimensions of the fuse structure.

A more specific object of the invention is the provision of a high powerfuse structure in which a conducting circuit through the arc passage isconstituted by a movable conducting member connected at one end to anend terminal of the fuse holder by a short fusible member of relativelysmall cross section and at the other end to the other end terminal byseparable contact means.

Additional objects and advantages will appear in the followingdescription, when read in connection with the accompanying drawing, inwhich:

Figure 1 is a longitudinal sectional view of the fuse structure of myinvention;

Fig. 2 is an enlarged elevation view partially in section of the refillunit of my fuse device; and

Fig. 3 is a cross sectional view of the refill unit taken along the lineIII-III of Fig. 2.

In general the fuse structure of my invention embodies a tubular fuseholder and a refill unit removably mounted therein of the general typeshown and described in the patent to H. L. Rawlins, No. 1,978,634,issued October 9, 1934, and assigned to the assignee of thisapplication.

Referring to the drawing, the fuse holder of my invention constitutes apair of spaced terminal members 5 and I of conducting material securedto the ends of a pair of concentric tubes 9 and II of insulatingmaterial. The inner tube 9 is threaded at its'ends for engagement withcorresponding internally threaded portions of the terminal members 5and 1. The outer tubular member H is adapted to be seated in an annularrecess i3 provided in the opposed end faces of the terminal members 5and 1. Thus the internal tubular member 9 is placed in tension whereasthe outer tubular member II is held in compression. The terminal member1 is provided with a bore 15 for the reception of a refill unit ll shownmore clearly in Fig. 2.

The refill unit I! comprises a metallic collar or ferrule l9 screwthreaded on to the lower end of a tubular casing 2| of insulatingmaterial. The interior of the tubular casing 2| is preferably lined witha gas producing insulating material, in this instance a plurality ofcompressed tubular blocks 23 of boric acid. The blocks 23 are supportedupon an annular ledge 25 of the ferrule [9 at the lower end of therefill unit and are held in compression by an annular closure member 21of insulating material such as hard fibre screw threaded into the upperend of the tubular casing 2 I. The openings through the compressedblocks 23, the ledge 25 and the annular member 21 are disposed inalignment and form an arc passage, indicated at 29. Disposed within thearc passage 29 is a rod-like conducting member 3| of slightly lessdiameter than the diameter of the passage. The lower end of rod 2| iselectrically connected to the ferrule I9 by a radially extending pin 33of fusible material, such as copper orsilver or any other materialhaving a high conductivity but a relatively low melting point. The lowerend of rod II- is also joined to the ferrule l9 by a diametricallydisposed strain pin 35, pref erably of steel or'other suitable materialhavin a high resistance and a high tensile strength. A sleeve 31 ofinsulating material disposed about the lower end of rod 3| serves as aspacer between the rod and the ferrule l9 and facilitates the assemblyof the pins 33 and 35. The upper end of the rod 3| is provided with anenlarged contact portion 39 and a threaded portion 4| of reduceddiameter, the purpose of which in each instance will appear more fullyhereinafter.

'When the refill unit I1 is disposed within the bore ii, the uppershoulder 43 of the ferrule I9 is adapted to engage the lower surface ofan inwardly extending flange 45 provided within the bore ii of theterminal member I. The ferrule i9 is firmly held in contactingengagement with the flange 45 by means of a tubular member 41 havingthreaded engagement with an appropriately threaded portion within thebore I5.

. the stop member 55.

The upper terminal member is provided with a bore 49 in which isdisposed an operating spring 5|. The spring 5! is secured at .its upperend to the spring support member 53 and at its lower end to a similarsupport member 55. The spring support 55 is screw threaded to thethreaded portion 4| of the rod 3! for joining the operating spring tothe rod. The upper end of the spring support member 53 has a threadedportion 5i of reduced diameter which is adapted to extend through anannular guide and stop member 59 which is preferably screw threaded intothe bore 59. A cap member 5i is screw threaded'on to the threadedportion 57, and maintains the spring support 53 in clamping engagementwith Thus, the spring 5i exerts a biasing force upon the rod 3| formoving it through the arc passage 29 in response to fusion of the pins33 and 35.

A sleeve 53 ofconducting material is threaded to the upper terminal 5and extends downwardly into the tubular casing member 9 of insulatingmaterial. Supported from the lower end of the conducting sleeve 63 are aplurality of yieldingly mounted contact fingers 55 disposed incircumferentially spaced relation to form a tulip type contact structureadapted to cooperate with the enlarged contact portion 39 of the rod 3i.The

contact fingers 55 are biased into contacting engagement with thecontact portion 39 by a coil spring t'l encircling the contact fingers.

From the foregoing description, it will now be apparent that anelectrical circuit exists through the fuse device from the upperterminal member 5 through the conducting sleeve 63, the contact fingers65, contact 59, rod 3!, fusible pin 35, ferrule l9, to the lowerterminal member I. The spring support members 53 and 55 are alsoelectrically connected in this instance by a plurality of flexibleconductors 65 secured by screws to the respective members as shown. Theflexible conductors 69, therefore, provide an additional conducting pathbetween the movable rod 3! and the upper terminal member a.

The operation of my fuse device is as follows: When the movable rod 3iis in the position, as

shown in Fig. 1;; 'currentfrom the terminal mem--.

her 5 may flow to the terminal member l by the path previously defined.In the event of an overload, the short section of the fusible pin 33between the rod 3i and the ferrule i9 fuses, thereby causing the currentto flow from the rod 3!! through the strain pin 35 to the ferrule i5.Since the strain pin 35 is of high resistance material, such as steel,it immediately fuses and permits the operating spring 5i to move the rod3! upwardly through thearc passage 29, thereby establishing an arebetween the ferrule 19 and the end of the rod. This are is quicklyextinguished by expulsive action which is well known,

resulting from the action of the are upon the arc passage lining 23 ofgas forming material. After moving a short distance in the upwarddirection, the contact portion 39 of the rod 3i moves out of engagementwith the contact fingers 65, thereby transferring the entire arc currentto the flexible conductors 69. The conductors 89 are so selected thatthey will carry the arc current on a severe overload during the arcingperiod, but do not have sufficient cross section to carry the normaloperating load of the fusedevice.

The greater portion of the normal load current in this instance iscarried by the separable contact structures 39 and 65. The provision ofthis separable contact structure permits the use of a operatedsuccessfully when the fuse pin 33 was constructed of silver having-aneffective fusible section of 1 6 inch in diameter and a length of ainch. The strain pin 35 in this instance was also approximately 1* inchin diameter and formed of steel. A fuse device constructed in thismanner operated in .0083 second while clearing a short circuit of 20,000amperes at rated voltage, and is equally as fast in operation as fusedevices normally rated at 300 amperes for the same operating voltage.

It will be noted that the fusible section of the 'pin 33, being thatsection of pin 33 which spans the short distance between operating rod3i and ferrule 59, is of materially less mass than that normallyemployed in fuse devices of thetype herein described. It is due to therelatively short length of this fusible section that it loses heat tothe ferrule l 9 and the operating rod 3i so rapidly that during normalconditions of load, it never reaches the fusion temperature. However, onoverloads, a large quantity of heat is generated so quickly that thesmall mass of the fusible sectlon is heated to the melting point beforethe heat can flow away to the adjacent elements. Because of theexceptionally small mass of fusible material, the operation of the fusedevice is particularly rapid and considerably faster in operation thanknown fuse devices using a larger fusible section. The strain pin 35 ofsteel is of such high resistance that following the fusion of thefusible pin 33, the pin 35 fuses even more quickly. Therefore, it haslittle effect in delaying the operation of the fuse.

In general, after a fuse operation, removal of the refill unitll fromthe fuse holder is accomplished by removing the clamping member ll andthe cap member M which permits the unit ii and the operating spring 5iwith its support members 53 and 55 to drop through the bore l5 at thelower end' of the holder. The spring support 55 is removed from theconducting rod 3! and screwed onto the conducting rod of a new refillunit if. A suitable reloading tool may then be secured to thethreaded-portion 57 and the new unit with the operating spring 5iattached is inserted in the holder through the bore Hi from the lowerend thereof. The clamping member ll and the cap 6! are then replaced inthe order named. For further details of construction of the refill unitand its associated operating mechanism as. well as the method ofreplacing such units, reference may be had to Rawlins Patent No.1,976,634 referred to above.

Although I have shown and described a particular fuse device, it is tobe understood that the same is for the purpose of illustration and thatchanges and modifications may be made by those skilled in the artwithout departing from the ispirit and scope of the appended claims.

I claim as my invention: v

1. In a circuit interrupter, a pair of spaced for interconnectingconducting means said terminal members, said including separablecontacts and a fusible section arranged in series relation and meansindependent of the are formed for separating said contact means inresponse to fusion of said fusible section.

2. In a circuit interrupter, a pair of spaced conducting tenminalmembers, conducting means for interconnecting said terminal members,said conducting means including separable contact means and a fusiblesection arranged in series relation, means for separating said contactmeans in response to fusion of said fusible section, and flexibleconducting means arranged in parallel relation with said separablecontact means and of less current carrying capacity than said contactmeans for carrying the arc current upon separation of said contactmeans.

3. In a circuit interrupter, a pair of spaced conducting terminalmembers, conducting means for interconnecting said terminal members,said conducting means including a movable contact member, separablecontact means connecting one of said terminal members with said contactmember, a permanent connection in parallel with said separable contactmeans and of less current carrying capacity than said contact means, afusible element connecting the other of said terminal members with saidmovable contact member, and means for moving said contact member uponfusion of said fusible element to elongate the arc caused by the fusionof said element and to separate said separable contact means to transferthe arc current to said permanent connection.

4. In a circuit interrupter, a tubular closure of insulating material, aconducting terminal member at each end of said closure, means definingan arc passage within said tubular closure, conducting means movablethrough said are passage to establish an arc therein, fusible meanselectrically connecting said conducting means with one'of said terminalmembers, separable contact means electrically connecting said conductingmeans with the other of said terminal members, a flexible conductingmeans connected in parallel with said separable contact means, andspring means responsive to the fusion of said fusible means for movingsaid conducting means through said arc passage to establish an arctherein and for separating said contact means to transfer the arccurrent to said flexible conducting means.

'5. In a fuse device, a stationary conducting member, a; movableconducting member having at least a portion thereof closely adjacent tobut ing said movable conducting member away from said stationaryconducting member, and fusible means spanning and electricallyconnecting said stationary and movable conducting members, the spanningportion of said fusible means having a cross section the greatestdimension of which is at least equal to the spanning length thereof.

6. In a fuse device, a stationary contact member having an aperturetherethrough, a movable conducting member having a portion thereofextending into said aperture, said portion having a cross-sectionsubstantially equal in area to that of said aperture, a pin of fusiblematerial electrically connecting the inner surface of said aperture withsaid portion of said movable conducting member, and means responsive tothe fusion of said pin for moving said movable member away from saidstationary member.

7. In a fuse device, a stationary contact member having a circularaperture therethrough, a

movable conducting rod one end of which extends into and substantiallyfills said aperture, a pin of low melting point fusible materialextending radially from said contact member into said conducting rod forelectrically connecting said contact member-and said conducting rod,spring means biasing said conducting rod away from said contact member,and a strain pin of greater tensile strength than said pin of fusiblematerial extending from said contact member to said conducting rod forholding said rod against movement by said spring means while said pin offusible material is in the unfused condition.

8. In a fuse device, a tubular closure of insulating material, aconducting terminal member at each end of said closure, a renewablerefill unit normally positioned within said closure, said refill unitincluding means defining an arc passage, a conducting member movablethrough said are passage and fusible means normally connecting one endof said movable member with one of said conducting terminal members,separable contact means normally connecting the other end of saidmovable member with the other of said conducting terminal members, andmeans within said tubular closure for releasably engaging and actuatingsaid movable conducting member through said are passage.

9. In a fuse device, a tubular closure of insulating material, aconducting terminal member at each end of said closure, means withinsaid closure defining an arc passage, a conducting rod movable throughsaid passage to establish an arc therein, fusible means normallyconnecting one end of said rod with one of said conducting terminalmembers, a plurality of contact fingers within said closure connected tothe other of said conducting terminal members, means for normallybiasing said contact fingers into engagement with the other end of saidconducting rod, flexible conducting means of lower current carryingcapacity than said contact fingers connecting said other terminal memberand said conducting rod, and spring means operative upon fusion of saidfusible means for moving said conducting rod through said are passageand for disengaging said contact fingers from said conducting rod totransfer the arc current to said flexible conducting means.

10. A refill unit for a fuse device comprising means defining an arcpassage, a conducting terminal disposed at one end of said are passage,a movable conducting member in said passage, fusible means normallyconnecting said movable spaced from said stationary member, meansbiasmemberwith Said terminal and a Contact secured to and movable withsaid conductingmember to enable a separable circuit connection to bemade with said conducting member.

11. A refill unit for a fuse device comprising means defining an arcpassage, a conducting terminal disposed at one end of said are passage,a movable conducting member in said passage, fusible means normallyconnecting one end of said movable member with said terminal, the otherend of said conducting member extending exteriorly of said are passage,and a contact carried by the exteriorly extending portion of saidconducting member, said exteriorly extending portion having amechanically engageable portion adjacent to said contact.

12. In a fuse device, a stationary contact member having an aperturetherethrough, a movable conducting member having a portion thereofextending into said aperture, said portion having a. cross-sectionsubstantially equal in area to that of said aperture, said membersrespectively co prising substantial masses of electric and heatconducting material, a pin of fusible material electrically connectingthe inner surface of said aperture with said portion of said movableconducting member, and means responsive to the fusion of said pin formoving said movable member away from said stationary member.

13. In a fuse device, a stationary conducting member, a movableconducting member having at least a portion thereof closely adjacent tosaid stationary member, fusible means electrically connecting saidstationary and movable conducting member, and means biasing said movableconducting member for movement away from said stationary conductingmember the largest cross sectional dimension of said fusible means beingon the order of the distance between said members.

14. In a fuse device, a stationary conducting member, a movableconducting member having at least a portion thereof closely adjacent tosaid stationary member, fusible means electrically connecting saidstationary and movable conducting members, strain means mechanicallyconnecting said stationary and movable conducting members, and meansbiasing said movable conducting member for movement away from saidstationary conducting member in a manner to. stress said fusible andstrain means substantially entirely in shear,

15. In a fuse, separable terminals having portions normally maintainedin closely spaced relation by a fusible connection, said connectionhaving across sectional area such as to be fused substantiallyinstantaneously by the heat developed by the passage of normal loadcurrents therethrough when dissociated from said terminals, and at leastone of said terminals comprising a sufficiently large mass of heatconducting material to conduct the heat developed in said fusibleconnection by normal load currents away from said fusible connectionfast enough to prevent fusion thereof, but ineffective to conductsufficient heat away from said fusible connection to prevent fusionthereof upon the passage there through of currents of a predeterminedhigher value.

16. In a fuse, separable terminals normally maintained againstseparation by a fusible connection, said connection having across-sectional area such as to be fused by the heat developed by thepassage of currents therethrough of a value substantially below normalload currents when dissociated from said terminals, and at least one ofsaid terminals comprising a sufiiciently large mass of heat conductingmaterial positioned relative to said connection in a manner to conductthe heat developed in said fusible connection by normal. load currentsaway from said fusible connection fast enough to prevent fusion thereof,but ineffective'to conduct sufficient heat away from said fusibleconnection to prevent fusion thereof upon the passage therethrough ofcurrents above said normal load currents.

17. In a circuit interrupter, a pair of spaced conducting'terminalmembers, conducting means for interconnecting said terminal members,said conducting means including separable contact means and a fusiblesection arranged in series relation, and resilient means for separatingsaid contacts in response to fusion of said fusible section.

18. In a circuit interrupter, a tubular casing of insulating material,terminals at opposite ends of said casing, means of conducting materialassociated with one of said terminals and extending in one end of saidcasing, a movable rodlike contact, fusible means connecting said contactto the other of said terminals, separable conducting means one of whichis movable with said rod-like contact for electrically connecting saidrod-like contact and said means of conducting material, and meansbiasing said rod-like contact awayfrom said other terminal to draw outthe are upon fusion of said fusible means and separate said separableconducting means.

19. In a circuit interrupter, a pair of spaced conducting terminalmembers, conducting means for interconnecting said terminal members,said conducting means including separable contacts associated,respectively, with one of said terminal members and a movable rod-liketerminal, fusible means connecting said rod-like terminal with the otherof said terminal members, and resilient means biasing said rod-liketerminal for movement to elongate the are formed upon fusion of saidfusible means and to separate said separable contacts.

20. In a circuit interrupter, a tubular casing of insulating material,terminals at opposite ends of said casing, tubular means ofconducting-material associated with one of said terminals and extendingin one end of said casing, a movable rod-like contact in said casing,fusible means connecting said contact to the other of said terminals,separable conducting means one of which is movable with said rod-likecontact for electrically connecting said rod-like contact and saidtubular means of conducting material, and means in said casing biasingsaid rod-like contact away from said other terminal to upon fusion ofsaid fusible means and separate said separable conducting means.

21. In acircuit interrupter, a tubular casing of insulating material,terminals at opposite ends of said casing, means of conducting materialassociated with one of said terminals and extending in one end of saidcasing, a movable rod-like contact, fusible means connecting saidcontact to the other of said terminals, separable conducting means oneof which is movable with said rodlike contact for electricallyconnecting said rodlike contact and said means of conducting material,and spring means connected between said one terminal and said rod-likecontact for biasconducting means.

22. In a circuit interrupter, a tubular casing of insulating material,terminals at opposite ends means and separate means.

JAMES M. WALLACE.

draw out the arc' DISCLAIMER 2,259,946.James M. Wallace, Braddock, Pa.CIRCUIT INTERRUPTER. Patent dated October 21', 1941. Disclaimer filedMarch 5, 1943, by the assignee,

Westinghouse Electric c5: Manufacturing Company. Hereby enters thisdisclaimer to claims 1, 17 and 19 in said patent.

[Ofiicial Gazette March 30, 1943.]

DISCLAIMER 2,2 59,9 16.James 1M. Wallace, Braddock, Pa. CIRCUITINTERRUPTER. Patent dated October 21, 1941. Disclaimer filed May 3,1944, by the assignee, Westinghouse Electric Manufacturing Company.

Hereby enters this disclaimer to claims 2, 3, 4, 10, and 11 of saidpatent.

[Ofiicial Gazette May 80, 1.944.]

DISCLAIMER 2,259,946.James M. Wallace, Braddock, Pa. CIRCUITINTERRUPTER. Patent dated October 21', 1941. Disclaimer filed March 5,1943, by the assignee,

Westinghouse Electric da- Manufactum'ng Company. Hereby enters thisdisclaimer to claims 1, 17 and 19 in said patent.

[Oficial Gazette March 30, 1.943.]

DISCLAIMER 2,259,946.James M. Wallace, Braddock, Pa. CIRCUITINTERRUPTER. Patent dated October 21, 1941. Disclaimer filed May 3,1944, by the assignee, Westinghouse Electric d2 lllanufacturing Company.Hereby enters this disclaimer to claims 2, 3, 4, 10, and 11 of saidpatent [Official Gazette May 80, 1.944.]

